Lunsumio (Mosunetuzumab): What I Learned Researching My Own Next Treatment

 

Geumgyeguk wildflowers along the Blue Road trail, Yeongdeok — South Korea

 

When I searched for information about Lunsumio as a relapsed Follicular Lymphoma patient, I found press releases from pharmaceutical companies. Clinical trial summaries written for oncologists. Almost nothing written by or for patients.
 
So I researched it myself. This is what I found.
 

Who I Am and Why I Wrote This

I have Stage 4 Follicular Lymphoma, Grade 3A. Diagnosed February 2021. R-CHOP for first-line treatment. Obinutuzumab plus Bendamustine for second-line. Now on my second relapse.
 
Lunsumio is my next planned treatment.
 
If you are in a similar position — waiting for this drug, researching it, trying to understand what it actually does — this post is for you.
 

What Is Lunsumio?

Generic name: Mosunetuzumab
Manufacturer: Roche
Korea MFDS approval: November 2023
 
Lunsumio is a bispecific antibody.
If that term is new to you, here is the simplest way to understand it.
 
Your body already has immune cells that are capable of killing cancer cells. They are called T cells. The problem is that cancer cells are good at hiding — T cells often fail to recognize them as a threat.
 
Lunsumio acts as a bridge.
 
One hand grabs a T cell. The other hand grabs a cancer cell (specifically, a protein on its surface called CD20). It physically brings them together — forces them face to face — and the T cell destroys the cancer cell directly.

Traditional treatment: "There's a cancer cell somewhere. Immune system — go find it."
Lunsumio: "Immune system — I'm bringing you right to the cancer cell. Right now."

→ For a fuller explanation of how bispecific antibodies work, see: [What Is a Bispecific Antibody?] (link coming soon)
 

How Is This Different from Previous Treatments?

Traditional chemotherapy — R-CHOP, Bendamustine — works by attacking cancer cells with toxic agents. The problem is that healthy cells get caught in the crossfire. That is where side effects like hair loss, nausea, and immune suppression come from.
 
Lunsumio works differently. It uses your own immune system rather than chemical toxicity.
 
There is another practical difference worth knowing.
 
You do not need to be hospitalized.
 
There is a similar immune therapy called CAR-T, which involves removing your own T cells, genetically engineering them in a laboratory, and reinfusing them. That process takes weeks and requires inpatient care.
 
Lunsumio is a ready-made drug. You receive it as an injection at an outpatient clinic and go home the same day.
 

What Do the Numbers Say?

The key data comes from the pivotal phase 2 GO29781 trial (NCT02500407), which studied 90 patients with Follicular Lymphoma who had relapsed at least twice.

• Complete response rate: 60% — in 6 out of 10 patients, cancer became undetectable
• Overall response rate: 77.8% — in approximately 8 out of 10 patients, some measurable response occurred
• Median time to response: approximately 1.4 months — relatively fast

[Lancet Oncology, 2022 — original trial results]

3-year follow-up (Blood, 2025):
Updated data published in the journal Blood confirmed that a significant proportion of patients who achieved complete response were still in remission at 3 years. Median duration of response was 35.9 months. The median overall survival had not been reached, and 82.4% of patients were alive at 36 months.
[Blood, 2025 — 3-year follow-up data]
 
5-year follow-up (ASH 2025):
At the 2025 American Society of Hematology annual meeting, 5-year data from the same trial was presented. Complete response rate and overall response rate remained consistent at 60% and 78% respectively, with durable long-term responses confirmed.
[ASH 2025 — 5-year data summary]

One more detail that matters to me personally.
 
More than half of the patients in this trial were in the "POD24" category — meaning their disease progressed within 24 months of initial diagnosis. This is considered a high-risk group with generally poorer outcomes.

I am in that category.

Seeing those response rates in a population that includes a majority of high-risk patients was the first time I felt something close to hope about this treatment.
 

How Is It Administered?

• One cycle = 21 days
• Standard duration: 8 cycles
• If complete response is not achieved by cycle 8, treatment can be extended to a maximum of 17 cycles
• Administered as an injection at an outpatient clinic — no hospitalization required
• Early cycles are monitored carefully for cytokine release syndrome (CRS) — an immune reaction that can cause fever, chills, and flu-like symptoms. Generally manageable, but requires observation

 

Can You Get It in Korea Right Now?

Approved — yes. Insurance covered — no.

Lunsumio received Korean MFDS approval in November 2023. It was even the first drug approved through Korea's GIFT program, a fast-track review process for innovative therapies.
 
Insurance coverage review began at the same time as approval. As of May 2026, it is still not covered.
 
The current government position on bispecific antibodies as a class is cautious — citing insufficient long-term data. Several similar drugs have failed the coverage review process.
 
Lunsumio's strongest argument for coverage is that it now has 5-year follow-up data — the longest of any drug in its class. Whether that is enough remains to be seen.
 
When coverage will happen — I genuinely do not know. The timeline keeps shifting. It was supposed to be 2025. Then 2026. 2025 has passed. 2026 is almost halfway through.
 

What Does It Cost Without Insurance?

The cost of Lunsumio without insurance coverage varies by hospital and is not publicly listed.
 
My oncologist gave me an estimate of approximately 25 million KRW per cycle — roughly $18,000–19,000 USD.
 
For context: the standard treatment course is 8 cycles minimum.
 
This is why I am waiting.
 

Where I Am Now

PET-CT confirmed disease progression.
My five-year rare disease registration has been renewed. 
 
Symptoms are manageable. No major functional impairment.

The disease is present — I can feel it in places — but it is not stopping me from living.
 
My current strategy is to maintain my condition as long as possible through diet and movement, while waiting for either insurance coverage or another treatment option to become available.
 
Describing "waiting" as a treatment strategy feels strange to write. But right now, it is the most rational choice I have.
 

For Anyone in a Similar Position

This post was written by a patient, for patients.

I am not a medical professional. This is a summary of publicly available information, organized from a patient's perspective. Please discuss all treatment decisions with your oncologist.

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This post reflects my personal experience and publicly available information only. It does not constitute medical advice.